Immunocytochemical method for the detection of terminal deoxynucleotidyl transferase in acute leukemia.

Terminal deoxynucleotidyl transferase (TdT) has become an important marker for the classification of acute leukemias. Originally detected by a biochemical assay, the presence of this enzyme in leukemia can now be detected by making use of a highly specific antibody and by applying the immunofluorescence method. In this study, an attempt was made to apply the unlabeled peroxidase-antiperoxidase (PAP) technique for the examination of TdT positive cells. We have optimized this method and have compared the different assays - biochemical, immunofluorescence, and immunocytochemical (PAP) - in ten patients with acute leukemia. The results obtained from all three methods are in accordance with one another, but the PAP method is a further simplification for the detection of TdT in the routine diagnostic of acute leukemias.